72 F100 recommended RPM? Tuning Eddy w/ vac gauge...


Asked by May 10, 2016 at 11:23 PM about the 1972 Ford F-100

Question type: Maintenance & Repair

Trying to tune my 72 F100 in w/ vac gauge and tachometer. The vac doesn't increase past 6 turns on each mixture screw. For some reason, it runs ok in park, then is rough in drive. Is there a recommended RPM I should aim for in park and drive? C4 trans.

4 Answers


It's a 1406 Edelbrock 600 CFM btw


Way back when we just turned the mixture screws for highest rpm at engine idle and then turned them out an additional 1/8 to 1/4 of a turn. Not sure if that is the correct procedure, but it seemed to work. Spark plugs wires and other ignition parts need to be in good working order for the carb adjustment to work properly. I would think 700 to 800 rpm in Park would be good.


Screw the vacuum gauge, If everything is good, no vacuum leaks, the gauge will show 15 to 18 inches per square pounds. Use your tack. Start by screwing in the idle mixture screws until they stop, then back them out 1 1/2 turns, then start the engine. From this point you adjust the idle mixture screws in or out (more than likely out) to the highest RPM you can get out of them, adjusting the idle to keep it at 650 RPM's when you do. Once you cannot get any more RPM's out of the idle mixture screws from 650 RPM (idle) turn them out further 1/4 turn for proper air/fuel mixture.

1 people found this helpful.

Good job Rowefast, I forgot about turning the screws out 1 1/2 to 2 turns from the bottom.

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